The invention relates to a method for preventing the inoperability of an open-end spinning rotor arrangement, which has a rotor with a fiber collecting groove. A hub is provided into which a rotor shaft is pressed. The free end of the rotor shaft has a step bearing surface which is arranged at a predetermined distance from the fiber collecting groove.
It is known from German Patent Document DE-A 27 16 573 to radially support the spinning rotor assemblies, which are formed by a rotor and a rotor shaft, by means of a supporting disk bearing assembly for the rotor shaft. The rotor shafts are supported in the axial direction by means of a step bearing which contains a ball excited to perform vibrations on which the free end of the shaft is supported by means of a step bearing surface. Previously, spinning rotors of this type became unusable after extensive usage because the rotor was worn out particularly in the area of the fiber collecting groove. However, recently, this wearing of the rotors has been significantly reduced by the fact that the rotors were made of steel and, in the area of the interior of the spinning rotor, were subjected to a special treatment and were provided with an additional coating. It was found in practice that these open-end spinning rotors now become unusable in a different manner, specifically that a wearing takes place in the area of the step bearing surfaces of the rotor shafts. This wearing which may differ considerably at the individual spinning points, has the result that the rotor changes its position in the axial direction so that then the adjusted distances to a fiber feeding duct and particularly to a yarn withdrawal nozzle, which influence the spinning result, will also change. Although it is known from German Patent Document DE-A 27 16 573 to equip the end of the rotor shaft with an exchangeable projection which has a step bearing surface, the exchange of this projection in order to prevent a wearing-out requires high technical expenditures, is expensive and, under certain circumstances, may also have the result that the concentricity of the open-end spinning rotor may change and it must then be balanced again.
It is an object of the invention to provide a method for preventing the wearing-out of an open-end spinning rotor which is simple and can be carried out without major expenditures.
This object is achieved according to the invention in that the operability of the open-end spinning rotor is restored after a wearing-out of the step bearing surface by means of an axial shifting of the shaft in the hub of the rotor so that the distance between the fiber collecting groove and the step bearing surface is restored to a predetermined value.
By means of the method and apparatus according to the invention, it is possible to restore the operability of the open-end spinning rotor in a simple manner without the risk of ovalization. Practice has shown that the hub length and thus the length of the press fit, as a rule, is overdimensioned so that a slight axial shifting of the rotor shaft, as it is required for compensating the wear, does not reduce the tightness of the press fit.
In order to permit a repeated restoring of the operability of the rotor assembly, it is provided in a further development of the invention that, in the case of a rotor shaft that is still new, the front end of the rotor shaft facing away from the step bearing surface projects over the hub in the axial direction toward the interior of the rotor.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.